Recording Guitar with a DI [2010 thread revived]

[mobu]

Here's the chain I am using for recording my electric Les Paul guitar:

Guitar --> ARTcessories Zdirect (DI Box) --> PreSonus Firebox (audio interface)

I am using Native Instrument's Guitar Rig 4 as the processor.

The problem is whatever guitar settings I use in Guitar Rig, I get a low noise / hissing sound. Sometimes it sounds good and vintage but I just want a clean and neutral sound. What should I do?

[vurt]

have you tried recording to a dry audio track?
is the noise present here?

if we can eliminate this possibility its not the hardware and is something to do with inputting to gr.

[obstgegenrechz]

does the DI box have a ground-lift? and what happens if you engage it?

[mobu]

does the DI box have a ground-lift? and what happens if you engage it?

Yeah it does have a ground lift..it also has a Filter and an attenuator. I haven't tried them coz I just got the DI.

[rectus_dominus]

Quick question: What is the cheapest way to lower my guitar's impedance to the PC integrated soundcard's line level? I'm not an electrician, so no DIY please
I'm looking for cheaper suggestions than a $150 E-mu 0202
Thanks, cheers!

[C00kie]

@ Mobu: there will always be some low-level background noise (less than -70dB) in guitar recordings. Some people use a noise gate or process the dry track with a noise suppression plugin.

@ Rectus: Cheap DIs can be had from $25 and up. You don't only need impedance conversion, but also about 20dB of gain. Most DIs only do attennuation since they are designed to connect to a mic input and not a line input.

[mobizoid]

I use a Digitech RP155 in bypass mode. Works great. Dead silent stereo outputs into my Audio interface. You can get used ones very cheap now days. I am sure there are other Digitech (and other brands) models, you could use to the same effect.

[Compyfox]

I'm certainly no expert in this (no guitarist - "just" a tech/AE), but I recently had this topic a couple of times with friends and clients. So maybe I can help out with some knowledge bits.

Here's the chain I am using for recording my electric Les Paul guitar:

Guitar --> ARTcessories Zdirect (DI Box) --> PreSonus Firebox (audio interface)

...

The problem is whatever guitar settings I use in Guitar Rig, I get a low noise / hissing sound. Sometimes it sounds good and vintage but I just want a clean and neutral sound. What should I do?

I did a quick dive at the tech specs of these devices, and the first question that comes to mind would be:
"Why not use the Instrument input of the Firebox directly but rather go for a Passive DI?"

The reason is simple: Impedance Conversion.
So unless you're using a real guitar amp in parallel, then you should always go the shortest route. Ideally an ADC with Hi-Z Input, or anything active with Hi-Z Input rather than a passive DI.

REASON: Low feeds High


On top of that, it is recommended to have a high Impedance for all kinds of guitars. 500k Ohm at bar minimum, ideally 1M Ohm. For acoustics (piezo's) even higher. What comes out at the output (can be anything from 150Ohm to 1k Ohm) is not that important - as long as the next input is definitely higher.

The ART ZDirect only offes 50k Ohm as Input Impedance. This could be the first culprit for noise, as the signal you get to work with is fairly low to begin with. So the only way to maybe check if the noise is gone, if you use the ground lift - but not(!) the attenuation switch.

If you still have noise, then I'd check a couple of other things.
Like: Does your ADC pick up radiating noise? Do you hear "HDD clicks" or your PSU (especially on laptops, this is a pulsing noise). Did you record your guitar nearby radiating devices like fluorescent lightbulbs, speakers, smart phones, etc. If you could rule all that out, then maybe try to get rid of the passive DI.

Unless that noise is really below -65dBFS (digital), then a noise gate should work for the quiet parts.

Quick question: What is the cheapest way to lower my guitar's impedance to the PC integrated soundcard's line level? I'm not an electrician, so no DIY please
I'm looking for cheaper suggestions than a $150 E-mu 0202
Thanks, cheers!

Unless the ADC/DAC comes with a Hi-Z Input (check the specs), you won't get past a DI. And as mentioned, DI's don't cost you an arm and a leg. Again - the higher the input impedance (again, check the specs), the better. Active DI boxes offer that right off the bat, passive ones might need some searching and higher investment.

Actually, in theory you can even use a basic guitar boost pedal as impedance converter. As long as this one is "active" (read: powered, which can be anything really - including an active volume pedal!), then you can connect your guitar directly to the line port (Guitar -> Pedal FX -> Line). It's a "ghetto" solution, but it works.

If you already have the E-MU 0202 - you have a Hi-Z Input with 1M Ohm (just checked the specs).

@ Rectus: Cheap DIs can be had from $25 and up. You don't only need impedance conversion, but also about 20dB of gain. Most DIs only do attennuation since they are designed to connect to a mic input and not a line input.

Invest 10 bucks more and get an active DI (street price are 30-40USD for noname ones), and all your troubles are gone. Once more: high input impedance right off the bat.

Again, if your recording module does feature high impedance (or hi-Z) balanced/unbalanced inputs, there is no need for a DI. And even then, you must ask yourself "do I really need one? Does the signal need to be converted from unbalanced into balanced?! Can I get away with a pedal FX?!" (see bullet points below)

Doesn't have anything(!) to do with a 20dB gain boost. Read the article I linked to above regarding signal flow. You don't need a preamp - unless we're talking microphones or acoustic guitars.



Summed up (very roughly spoken):
- Check the tech specs of your devices.
- look for at least 500k Ohm or 1M Ohm as Input impedance (passive ones, unless you go for really expensive ones, usually only feature up until 250k Ohm)
- if your ADC doesn't have a Hi-Z input, do you maybe have a preamp, an active DI or an active pedal FX at hand that could work as Impedance converter?
- if you only use your PC as "ITB amp solution", and your recording device offers a Hi-Z Input of some sorts, there is no need for a DI (read former point)
- a DI box (or even just a plain split box) in between your Guitar and ADC is only needed, if you want to record both the dry signal of your guitar, and the amp (picked up with a microphone)
- on that behalf: Conversion from Unbalanced to Balanced is only needed if you insist on connecting your guitar to a XLR port (unless that is a combi port), or if you want to run your signal through a mixing console



I hope that helps for the time being.

[khanyz]

I use a Digitech RP155 in bypass mode. Works great. Dead silent stereo outputs into my Audio interface. You can get used ones very cheap now days. I am sure there are other Digitech (and other brands) models, you could use to the same effect.

The RP155 has a USB Audio Interface. I haven't used mine in a while but I think it can record 24/44.1kHz via USB.

BTW I have an ART Z-Direct and it's input impedance is a little low for a guitar. You need an active DI ideally (I recommend Orchid Electronics as they are top quality at a stupid price and you can order them modded, such as custom transformers, at good pricing). Even if your Audio interface has an instrument input, a good active DI can improve things. The only interface that has had an instrument input I've liked is the Mindprint TRIO (but that was designed by Hughes & Kettner so no surprise at its quality).

[Compyfox]

Sorry if this comes out of nowhere, but...

You need an active DI ideally (...). Even if your Audio interface has an instrument input, a good active DI can improve things.

Can you maybe elaborate on that?

Why is an Active DI on top of an already existing Hi-Z input needed?
What things are "improved" with a so called "good DI"?

I want to understand this from a technical viewpoint.
We're both talking about 1MOhm impedance here and the only main difference (IMO) would be a frequency linearity with certain devices. But then again, that would IMO only matter if we talk about clean guitars and acoustic guitars.

But I've read these comments several times "always go for a DI", "a DI is always superior", etc.
Just... why? If DI's are ultimately superior just for impedance conversion, then why built these converters "into" a ADC?


Again - for understanding the technical viewpoint.

[khanyz]

Can you maybe elaborate on that

I meant a good DI to use instead of (so into the Mic or Line input) any inbuilt instrument input.

Impedance, and matching is all about giving the next stage in the gear chain the optimum combination of voltage and current. However, even though they both use Ohms as the unit, resistance and impedance are different things. You can think of resistance as a static property which affects current and voltage but impedance is more of a dynamic, reactive property so the whole circuit, including what you connect, combine to produce the output and feedback to it. Consequently, the actual value, and it's stability, is dependent on the combination of guitar/instrument and DI. Cheap DIs/Audio Interfaces, can give a 1MOhm value but react badly when something is plugged in. Better DIs are designed to be less dependant on what's plugged in and so have a more stable impedance. Some (like Radial) even have a knob to change this reactance to best suit what's connected.

Pickups are voltage machines but when connected to a load (i.e. circuit), the voltage can drop as current increases (Power is the constant). A high impedance lowers the current and maximizes the voltage. The pickup optimum is the right level of all three (high voltage and impedance, low current). This may not be the same as the input so they need to be converted without either side knowing.

Sorry, but some of that is an over simplification for clarity. In proving it wrong you'll understand what I meant, or should I go more technical (Ohm's law/equations, not Kirschhoffs)?

[stillshaded]

I don't get it.. the firebox doesn't need a DI box, why are you using one?

[Googly Smythe]

I almost offered my advice here (make sure the input to GuitarRig (or any amp sim) is not to high, etc) until I saw that the op was five years ago!
Still, last few posts contain many useful pearls of wisdom. Electronics is still a black art to me.

[khanyz]

I almost offered my advice here (make sure the input to GuitarRig (or any amp sim) is not to high, etc) until I saw that the op was five years ago!
Still, last few posts contain many useful pearls of wisdom. Electronics is still a black art to me.

Yeah, it was the RP155 comment that sucked me in. I loved mine but had my head turned by a Mustang.

Electronics is like lego, you just need to learn the blocks, how they combine and then how to (neatly) snap them to get what you really want. I did it as a hobby when I was a kid then specialized in it for my physics degree. Knowing it has always been handy but can quickly piss off sales assistants .

[Compyfox]

This thread is 5 years old?!

I think it's time that KVR gets a system, where such old treads are automatically tagged as "revive".

Impedance, and matching is all about giving the next stage in the gear chain the optimum combination of voltage and current. However, even though they both use Ohms as the unit, resistance and impedance are different things. You can think of resistance as a static property which affects current and voltage but impedance is more of a dynamic, reactive property so the whole circuit, including what you connect, combine to produce the output and feedback to it. Consequently, the actual value, and it's stability, is dependent on the combination of guitar/instrument and DI. Cheap DIs/Audio Interfaces, can give a 1MOhm value but react badly when something is plugged in. Better DIs are designed to be less dependant on what's plugged in and so have a more stable impedance. Some (like Radial) even have a knob to change this reactance to best suit what's connected.

In all seriousness - unless we talk about a >150USD module that is not even a breakout box, does it even matter these days?!

I do understand that better parts ultimately add to the stability of a signal, and therefore less frequency loss. But this whole thing currently reminds me of the year-old debates like "only an expensive ADC/DAC is a good ADC", and look how far this developed in less then a decade. Especially with companies like RME, Focusrite and Presonus.

Sorry, but some of that is an over simplification for clarity. In proving it wrong you'll understand what I meant, or should I go more technical (Ohm's law/equations, not Kirschhoffs)?

I think going full technical and mathematical (Ohms Law comes to mind), we'd only start to confuse people. Especially non techs. And I'm far too long out of this myself.


I currently don't have a ADC with built in Hi-Z inputs, only XLR in. So I'm using a preamp with built in high impedance input for "DI" usage. But if there is a Hi-Z input at pretty much all modern ADC/DAC's these days, why not simply use this port? Especially if it's a mid-class priced module.


You see, I just try to offer an easy-to-understand viewpoint here, while trying to evade the sometimes often involved snake oil. Especially if you say "always use a dedicated DI", but don't go more in-depth as to why.